1. Field of the Invention
The present invention relates to a powder metallurgy product and a method for producing the powder metallurgy product.
2. Description of the Background
In powder metallurgy, after some kinds of powders are mixed at a predetermined ratio, the mixed powder is formed into a desired shape under pressure and then sintered to be a final metallurgy product.
One of the advantages of powder metallurgy products is that machining operation is not necessary because powder metallurgy products having a substantially final shape may be formed in dies without machining operation. Recently, higher precision and more complex shapes have been required. Accordingly, machining operations have been required even for powder metallurgy products. However, generally, powder metallurgy products have poor machinability.
Japanese Examined Patent Publication (kokoku) 56-45964 (hereinafter referred to as the "'964 publication") discloses steel powder having good machinability. The contents of this application are incorporated herein by reference in their entirety.
In the steel powder disclosed in the '964 publication, the steel powder contains S of 0.15 to 0.5 weight percent (wt %) and Mn of at most an amount greater than a Mn/S balance amount by 0.3 weight percent. Mn is used for combining with S. MnS is not easily oxidized after Mn combines with S.
Generally, powder metallurgy products have inferior mechanical strength. The reason is presumed that powder metallurgy products have many pores therein, because powder metallurgy products are produced by being formed under pressure and being sintered.